<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
      .current {
        background-color: red;
      }
    </style>
    <script src="jquery-3.3.1.min.js"></script>
  </head>
  <body>
    <div>添加类名</div>
    <div class="current">删除类名</div>
    <div class="current">切换类名</div>
    <script>
      $("div").click(function () {
        $(this).addClass("current");
        // $(this).addClass("current current1");
      });
    </script>
  </body>
</html>